As stated by Henderson et al in U.S. Pat. No. 6,964,334 which issued Nov. 15, 2005, it is common practice in lumber processing facilities such as sawmills to transport lumber over the top of sorter bins by overhead chain conveyors equipped with pusher lugs. Chain conveyors for the movement of lumber have links which each have an upstanding lug mounted thereon, spaced at intervals along the chain. Movement of the chain brings the lug into contact with the lumber, which is then urged in the direction of the running of the chain. When the lumber is located over a desired bin, a gate corresponding to that bin opens allowing the lumber to fall into that bin. Conventionally, a slider block is rigidly mounted to the chain where the pusher lugs attach to the chain to facilitate sliding translation of the lugs along the conveyor. Typically, fasteners attach the slider block to the chain, requiring that the chain links be pre-drilled where the slider blocks are to be fastened. Thus, the process of attaching the slider blocks to the chain is time consuming and costly.
Consequently Henderson et al disclosed a slider block that required no pre-drilling of the chain and no fasteners for mounting of the slider block onto the chain and pusher lug. The snap-on slider block provided for efficient installation and replacement of slider blocks. Henderson et al described the slider block as a length of resilient flanged channel having a cut-out in the lower web of the channel to accommodate mounting a flat bar journalled in the cut-out. The flanged channel had a length sufficient to cover the length of a base plate on which the flat bar was orthogonally mounted. The sides of the channel defined a cavity having a depth corresponding to the thickness of the base plate. A pair of flanges extended inwardly over the cavity from the sides of the channel so as to define a chain-receiving slot therebetween. The base plate mounted within the cavity. The base plate was welded to a chain so that when the base plate was mounted in the cavity the chain was mounted in and along the chain-receiving slot.
In the prior art applicant is also aware of U.S. Pat. No. 7,530,448 which issued May 12, 2009, to Henderson et al for Capped Lugs for Transfer Chains. Henderson et al describe each lug as having a cap defining a housing in which the lug is mounted, and wherein the housing is sealed around the lug to inhibit the entry of detritus into the housing.
A drawback of the snap-on slider block of U.S. Pat. No. 6,964,334 is that the lug is metal and rigidly mounted to the chain. Thus, in the event of jamming or collisions of boards on the chain conveyor causing damage to the lugs, especially if the lugs are older and fatigued, the metal lugs will bend making them unusable. Metal lugs which have been bent or otherwise deformed so that they are no longer useful must be cut off and replaced. This typically requires that initially the lug is cut off to leave a stub so that a snap-on slider block may still be mounted on the base plate and the conveyor can then be later repaired properly to replace the stub with a full size metal lug. The cutting off of the damaged lug requires, at least to the extent that applicant's are aware, a hot work permit for the use of the torch within the mill facility and so it is inconvenient to effect the repair.
It is preferable that, in the event of damage, that the lugs break off rather than deform and have to be cut off. Consequently the present invention provides a combination slider block and lug which snaps into place over the base plate welded to the transfer chain either in the case of new chains where all the slider blocks and lugs are of the snap-on design according to the present invention, or in the case where a lug is damaged, once the damaged lug has been entirely removed. In either case the snap-on combination slider blocks and pusher lug is intended to snap off, rather than bend or deform, in the event of a damage-causing event.